In recent years, increasing concerns over fuel economy and environmental sensitivity have driven the transportation industry to develop new technologies to address these concerning issues. In fuel injection systems, fuel economy and emissions are driven by fuel injection characteristics. For example, the start, end, duration, and rate of fuel injection vary according to machining tolerances, aging, fuel properties, and fuel pressure measurement. The variability in fuel injection causes a corresponding variance in the exhaust emissions, power, and fuel consumption. Measuring the fuel injection characteristics allows for a closed loop control to reduce the variability, emissions and fuel consumption and to better optimize combustion for different operating fuels.
Fuel properties have a large influence on engine performance and fuel consumption. The variation in diesel alone at the local pumping stations can vary fuel consumption by up to 4% and emissions of NOx, PM, CO, and HC by 12%, over 50%, 40%, and 17%, respectively. Typically, engine calibrations have assumed fuel properties of the operating fuel and therefore use the same injection timing conditions regardless if the engine is operating on diesel or biodiesel. From feedback on the injection and combustion characteristics, injection timing can be modified to optimize combustion for different fuels.
Future engines may use advanced combustion methods, such as homogeneous compression charge ignition (HCCI) and premixed charge compression ignition (PCCI). Advanced combustion engines are very sensitive to injection timing and combustion and require continuous adjustment of ignition timing. A combustion feedback mechanism is therefore required. Laboratory research engines studying advanced combustion typically use in-cylinder pressure transducers, which are expensive and require space in the combustion chamber.
Cavitation is a natural phenomenon that occurs when a liquid experiences a very rapid pressure drop from high pressure to relatively low pressure. This pressure drop causes cavities, or bubbles, to form inside the liquid, and these cavities are called “cavitation.” With a fuel injector, for example, the fluid inside the injector can approach 30,000 psi, and when it is injected into a spray chamber or combustion chamber of an engine the fluid pressure can drop to atmospheric levels in a matter of milliseconds. As a result of this pressure drop, the fluid flowing through the fuel injector cavitates in multiple locations inside the fuel injector, as well as in the spray chamber or combustion chamber immediately outside the nozzle of the fuel injector, as discussed above.
Therefore, what is needed is a fuel injection feedback device adapted to be implemented inside a fuel injector of an operating combustion engine.